"After many conversations with our doctors and [general manager] Koby [Altman] and much thought given to what is best for the team and my health, I need to step back from coaching for the time being and focus on trying to establish a stronger and healthier foundation from which to coach for the rest of the season.
"I have had chest pains and other troubling symptoms, compounded by a loss of sleep, throughout the year. Despite a battery of tests, there have been no conclusions as to what the exact issue is.
"While I have tried to work through it, the last thing I want is for it to affect the team. I am going to use this time to focus on a prescribed routine and medication, which has previously been difficult to start in the midst of a season. My goal is to come out of it a stronger and healthier version of myself so I can continue to lead this team to the Championship we are all working towards."
Lue, 40, has been dealing with an undisclosed illness throughout the 2017-18 NBA season. He did not coach the team in the second half of Saturday's game against the Chicago Bulls at United Center because of the issue, and it was the third time he's been absent. He missed a Dec. 21 win over the Chicago Bulls and a Feb. 6 loss the Orlando Magic.
Larry Drew will be the team's head coach on an interim basis.
Following Saturday's 114-109 win over the Bulls, LeBron James said Lue's health takes precedence over Cleveland's performance.
"I mean, he's the captain of the ship, so absolutely," James told reporters. "We worry about his health, obviously. That's way more important than this game of basketball. We know he's been doing everything he needs to do to stay healthy. Take even more measures to get himself right. Everything that's been going on with our year, it's just another one."
The Cavs have, at seemingly every point this season, been at less than 100 percent health—either on their roster or coaching staff. Lue's absence is coming at a time when the team is preparing to welcome back Kevin Love to the lineup. According to Joe Vardon of Cleveland.com, the All-Star forward hopes to return from a broken left hand at the end of this week.